Multicarrier-signal receiving apparatus and multicarrier-signal transmitting apparatus

ABSTRACT

A multicarrier-signal transmitting apparatus comprising a rotation-amount setting unit configured to set a phase rotation amount for each subcarrier of a plurality of subcarrier groups, the phase rotation amount being set with a setting selected from a first setting and a second setting, the first setting being such that the phase rotation amount is identical for a plurality of subcarriers within each subcarrier group, and the second setting being such that the phase rotation amount is identical for a plurality of subcarriers within a plurality of subcarrier groups; and a phase rotator configured to add a phase rotation to a data signal of said each subcarrier of said plurality of subcarrier groups based on the phase rotation amount.

This application is a Continuation of co-pending application Ser. No.13/753,215, filed on Jan. 29, 2013, which is a Divisional of co-pendingapplication Ser. No. 12/374,249, filed on Jan. 16, 2009, the entirecontents of which are hereby incorporated by reference and for whichpriority is claimed under 35 U.S.C. §120. Application Ser. No.12/374,249 is the national phase of PCT International Application No.PCT/JP2007/064257 filed on Jul. 19, 2007, under 35 U.S.C. §371, whichclaims priority under 35 U.S.C. 119(a) to Patent Application No. JP2006-198095 filed in Japan on Jul. 20, 2006. The entire contents of eachof the above-identified applications are hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to a multicarrier-signal receivingapparatus and a multicarrier-signal transmitting apparatus, andparticularly to a multicarrier-signal receiving apparatus and amulticarrier-signal transmitting apparatus that utilize cyclic delaytransmit diversity.

Priority is claimed on Japanese Patent Application No. 2006-198095,filed on Jul. 20, 2006, the content of which is incorporated herein byreference.

BACKGROUND ART

Recently, multicarrier transmissions utilizing CDTD (Cyclic DelayTransmit Diversity) have been proposed in which a multicarrier-signaltransmitting apparatus including multiple transmission antennas addsdifferent cyclic delays to transmission signals to be simultaneouslytransmitted from the transmission antennas (see Non-patent Document 1).When CDTD is used, the channel frequency selectivity always increases,thereby preventing the reception power from decreasing over the entirefrequency of a reception channel, and achieving excellent average BER(Bit Error Rate) characteristics in a receiving apparatus.

FIG. 11 shows a case where a signal is transmitted from transmissionantennas 1 a and 1 b included in a multicarrier-signal transmittingapparatus to a reception antenna 2 a included in a multicarrier-signalreceiving apparatus. As shown in FIG. 11, signals s1 and s2 arerespectively transmitted from the transmission antennas 1 a and 1 b, anda multiplexed wave thereof is received by the reception antenna 2 a. Themulticarrier-signal transmitting apparatus utilizing CDTD adds differentcyclic delays to the signals s1 and s2 to be respectively transmittedfrom the transmission antennas 1 a and 1 b.

FIG. 12 shows the configuration and the power of the reception signal.

FIG. 12 (a) shows an example state of subcarriers and OFDM symbols beingrespectively arranged along the horizontal and the vertical axesrepresenting frequency and time. As shown in FIG. 12, channel estimationsymbols P1 to P5 are arranged at every 6 subcarriers.

FIG. 12 (b) shows a state of the reception signal being distorted in thefrequency domains with respect to the power where the vertical and thehorizontal axes represent frequency and power. When a transmissionapparatus uses CDTD, the frequency selectivity increases as shown inFIG. 12 (b). Therefore, enhancement of the reception characteristics canbe expected.

-   Non-patent Document 1: IEICE technical report RCS2004-392,    “Application of Cyclic Delay Transmit Diversity to DS-CDMA using    Frequency-domain Equalization”, issued on March, 2005 by the    Institute of Electronics, Information and Communication Engineers.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Since the frequency selectivity increases in the multicarriertransmission method using CDTD, channel estimation errors occur uponchannel response estimation for subcarriers at which no channelestimation symbol is arranged when channel estimation symbols separatelyarranged in the frequency direction are used, thereby degrading thereception characteristics.

Means for Solving the Problems

A multicarrier-signal receiving apparatus according to one aspect of thepresent invention may include: a Fourier-transformer that performs aFourier transform on reception signals to extract subcarriers; a channelestimator that performs channel estimation on one of the extractedsubcarriers using channel estimation symbols included in a subcarriergroup to which the one of the extracted subcarriers belongs, thesubcarrier group including subcarriers to which an identical phaserotation is added upon transmission; and a channel compensator thatperforms channel compensation on data symbols included in the one of theextracted subcarriers using a result of the channel estimation performedby the channel estimator on the one of the extracted subcarriers.

As a result, different phase rotation amounts are added to subcarriergroups each including the adequate number of subcarriers upontransmission. Thereby, the multicarrier-signal receiving apparatus canperform channel estimation with the frequency selectivity beingincreased and the channel estimation errors being suppressed. Therefore,enhancement of the reception characteristics can be expected.

The multicarrier-signal receiving apparatus may further include acontroller that gives, to the channel estimator, an instruction on achannel estimating method according to a resource block to which the oneof the extracted subcarriers belongs, the resource block being a unit ofdemodulation processing in frequency and time directions.

In multicarrier-signal receiving apparatus, the channel estimator mayselect, for the channel estimation to be performed on the one of theextracted subcarriers, whether to use channel-estimation symbolsincluded in the subcarrier group to which the one of the extractedsubcarriers belongs or to use channel-estimation symbols included in aplurality of subcarrier groups including the subcarrier group to whichthe one of the extracted subcarriers belongs, based on the instructiongiven by the controller, and perform the channel estimation based on theselection.

As a result, the multicarrier-signal receiving apparatus can set a rangeof channel estimation symbols that the channel estimator uses forchannel estimation to a range including close channel response valuesbased on a resource block in which different phase rotation amounts areadded to subcarrier groups upon transmission or a resource block inwhich the same phase rotation amount is added thereto. Therefore, themulticarrier-signal receiving apparatus can perform channel estimationwith channel estimation errors being suppressed.

In the multicarrier-signal receiving apparatus, the controller gives, tothe channel estimator, an instruction on a channel estimating methodaccording to a physical channel included in the resource block.

As a result, the multicarrier-signal receiving apparatus can set a rangeof channel estimation symbols that the channel estimator uses forchannel estimation to a range including close channel response valuesbased on whether or not a resource block includes a particular physicalchannel in which different phase rotation amounts are added tosubcarrier groups upon transmission. Therefore, the multicarrier-signalreceiving apparatus can perform channel estimation with channelestimation errors being suppressed.

In the multicarrier-signal receiving apparatus, the controller gives, tothe channel estimator, an instruction on a channel estimating methodaccording to a transport channel included in the resource block.

As a result, the multicarrier-signal receiving apparatus can set a rangeof channel estimation symbols that the channel estimator uses forchannel estimation to a range including close channel response valuesbased on whether or not a resource block includes a particular transportchannel in which different phase rotation amounts are added tosubcarrier groups upon transmission. Therefore, the multicarrier-signalreceiving apparatus can perform channel estimation with channelestimation errors being suppressed.

In the multicarrier-signal receiving apparatus, the controller gives, tothe channel estimator, an instruction on a channel estimating methodaccording to a logical channel included in the resource block.

As a result, the multicarrier-signal receiving apparatus can set a rangeof channel estimation symbols that the channel estimator uses forchannel estimation to a range including close channel response valuesbased on whether or not a resource block includes a particular logicalchannel in which different phase rotation amounts are added tosubcarrier groups upon a transmission. Therefore, themulticarrier-signal receiving apparatus can perform channel estimationwith channel estimation errors being suppressed.

In the multicarrier-signal receiving apparatus, the channel estimatoraverages results of channel estimation performed using thechannel-estimation symbols, and regards the averaged result as theresult of the channel estimation on the one of the extractedsubcarriers.

In the multicarrier-signal receiving apparatus, the channel estimatorlinearly interpolates results of channel estimation performed using thechannel-estimation symbols, and regards the averaged result as theresult of the channel estimation on the one of the extractedsubcarriers.

A multicarrier-signal receiving apparatus according to another aspect ofthe present invention may include: a Fourier-transformer that performsFourier transform on reception signals to extract a subcarrier; achannel estimator that performs channel estimation on the extractedsubcarrier using a channel estimation symbol included in a subchannelother than that to which the extracted subcarrier belongs, thesubchannel being a unit of demodulation processing in a frequencydirection; and a channel compensator that performs channel compensationon data symbols included in the extracted subcarrier using a result ofthe channel estimation performed on the extracted subcarrier includingthe data symbols.

A multicarrier-signal receiving apparatus according to another aspect ofthe present invention may include: a Fourier-transformer that performsFourier transform on reception signals to extract a subcarrier; achannel estimator that performs channel estimation on the extractedsubcarrier using channel estimation symbols included in subcarriergroups included in a subchannel to which the extracted subcarrierbelongs, each of the subcarrier groups including subcarriers to which anidentical phase rotation is added, and the subchannel being a unit ofdemodulation processing in a frequency direction; and a channelcompensator that performs channel compensation on data symbols includedin the extracted subcarrier using a result of the channel estimationperformed on the extracted subcarrier including the data symbols.

A multicarrier-signal transmitting apparatus according to another aspectof the present invention may include: a rotation-amount setting unitthat sets thereto a phase rotation amount for each subcarrier; and aphase rotator that adds a phase rotation based on the set phase rotationamount to a data signal of each subcarrier. The set phase rotationamount is identical for each subcarrier group including a plurality ofsubcarriers, and a phase rotation amount difference among adjacentsubcarrier groups included in a resource block is determined accordingto the resource block that is a unit of demodulation processing infrequency and time directions performed by a receiving apparatus.

As a result, the multicarrier-signal transmitting apparatus can selectto use or not to use cyclic delay transmit diversity with the same phaserotation amounts being added to each subcarrier group for precisechannel estimation upon reception.

Effects of the Invention

Since different phase rotation amounts are added to subcarrier groupseach including the adequate number of subcarriers upon transmission, themulticarrier-signal receiving apparatus of the present invention canperform channel estimation with the frequency selectivity beingincreased and the channel estimation errors being suppressed.

Therefore, enhancement of the reception characteristics can be expected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing the configuration of amulticarrier-signal transmitting apparatus according to a firstembodiment of the present invention;

FIG. 2 is a schematic block diagram showing the configuration of arotator 14-1 according to the first embodiment;

FIG. 3 is a schematic block diagram showing the configuration of arotator 14-2 according to the first embodiment;

FIG. 4 shows an example of OFDMA signals according to the firstembodiment being grouped into subcarrier groups SG1 to SG4 to betransmitted;

FIG. 5 shows an example of OFDMA signals according to the firstembodiment being grouped into subcarrier groups SG5 to SG7 to betransmitted;

FIG. 6 is a schematic block diagram showing the configuration of themulticarrier-signal receiving apparatus according to the firstembodiment;

FIG. 7 shows a case where a channel estimator 37 according to the firstembodiment performs averaging in each subcarrier group upon channelestimation for each subcarrier;

FIG. 8 shows a case where the channel estimator 37 according to thefirst embodiment performs linear interpolation in each subcarrier groupupon channel estimation for each subcarrier;

FIG. 9A shows an example of transmitted signals according to a secondembodiment being divided into multiple resource blocks RB1 to RB9 in aframe;

FIG. 9B shows a case where a subchannel SC5 according to the secondembodiment corresponds to a resource block RB2 or RB7 in which CDTD isused;

FIG. 9C shows a case where a subchannel SC6 according to the secondembodiment corresponds to any one of resource blocks RB1, RB3 to RB6,RB8, and RB9 in which CDTD is not used;

FIG. 10A shows an example of transmitted signals according to a thirdembodiment being divided into multiple resource blocks RB11 to RB19 in aframe;

FIG. 10B shows a case where a subchannel SC7 according to the thirdembodiment corresponds to any one of resource blocks RB12, RB17, andRB18 each including a particular physical channel;

FIG. 10C shows a case where a subchannel SC8 according to the thirdembodiment corresponds to any one of resource blocks RB11, RB13 to RB16,and RB19 each including no particular physical channel;

FIG. 11 shows a case where signals are transmitted from a conventionalmulticarrier-signal transmitting apparatus including multipletransmission antennas to a conventional multicarrier-signal receivingapparatus; and

FIG. 12 shows the configuration and the power of conventional receptionsignals.

DESCRIPTIONS OF REFERENCE NUMERALS

-   10 scheduler-   11-1 to 11-24 channel-estimation symbol generator-   12-1 to 12-24 data mapper-   13-1 to 13-24 multiplexer-   14-1 to 14-24 rotator-   15-1 and 15-2 IFFT unit-   16-1 and 16-2 GI inserter and P/S convertor-   17-1 and 17-2 D/A convertor-   18-1 and 18-2 RF unit-   19-1 and 19-2 transmission antenna-   20 a and 20 b rotation-amount setting unit-   21-1 a to 21-25 b complex multiplier-   30 reception antenna-   31 RF unit-   32 A/D convertor-   33 symbol synchronizer-   34 FFT unit-   35 controller-   36 channel compensator-   37 channel estimator-   38 subchannel extractor-   39 demodulator

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

Hereinafter, a first embodiment of the present invention is explainedwith reference to the accompanying drawings. In the first embodiment,user data is transmitted while signals in each subcarrier group areadded a given phase rotation by a multicarrier-signal transmittingapparatus. A multicarrier-signal receiving apparatus performsinterpolation, such as averaging or linear interpolation, on channelestimation values in each subcarrier group, and thereby acquires achannel estimation result for a subcarrier by which a channel estimationsymbol is not transmitted. The multicarrier-signal receiving apparatusperforms demodulation after performing a channel compensation using thechannel estimation result to acquire the transmitted user data.

FIG. 1 is a schematic block diagram showing the configuration of amulticarrier-signal transmitting apparatus according to the firstembodiment of the present invention. The multicarrier-signaltransmitting apparatus includes a scheduler 10, channel-estimationsymbol generators 11-1 to 11-24, data mappers 12-1 to 12-24,multiplexers 13-1 to 13-24, rotators 14-1 to 14-24, IFFT (Inverse FastFourier Transform) units 15-1 to 15-2, GI (Guard Interval) inserters andP/S (Parallel/Serial) convertors 16-1 and 16-2, D/A (Digital/Analog)convertors 17-1 and 17-2, RF (Radio Frequency) units 18-1 and 18-2,transmission antennas 19-1 and 19-2.

The multicarrier-signal transmitting apparatus performs CDTD by addingcyclic delays to signals to be transmitted from the transmission antenna19-2, and not to signals to be transmitted from the transmission antenna19-1. In the first embodiment, the signals to be transmitted from thetransmission antenna 19-1 are not output to the rotators, and thesignals to be transmitted from the transmission antenna 19-2 are outputto the rotators. However, signals transmitted from the transmissionantennas 19-1 and 19-2 may each be output to different rotators. In thiscase, cyclic delays to be added to the signals transmitted from thetransmission antennas 19-1 and 19-2 are differentiated, therebyperforming CDTD.

Although the rotators add phase rotations instead of cyclic delays totransmission signals, differences in phase rotation amounts amongsubcarriers are set to be identical, thereby achieving the same effectas when cyclic delays are added. Additionally, the transmission antennas19-1 and 19-2 may be arranged in the same sector in the same basestation, in different sectors in the same base station, or in differentbase stations.

The scheduler 10 assigns user data input to the multicarrier-signaltransmission apparatus to data mappers 12-1 to 12-24 each performingprocessing for a corresponding subchannel. Specifically, subchannel-1user data among the total number of 24 subchannels is output to the datamapper 12-1. Subchannel-2 user data is output to the data mapper 12-2.Subchannel-3 user data is output to the data mapper 12-3. Likewise,subchannel-24 user data is output to the data mapper 12-24.Additionally, the scheduler 10 outputs a control signal for determiningphase rotation amounts to the rotators 14-1 to 14-24.

A subchannel is a frequency band to be a unit of scheduling. There are24 subcarriers in the first embodiment. In the multicarrier-signalreceiving apparatus, the subchannel serves as a unit in the frequencydirection for demodulation processing.

The channel-estimation symbol generator 11-1 generates channelestimation symbols that are known symbols of the subchannel 1. Thechannel-estimation symbol generators 11-2 to 11-24 perform similarprocessing with respect to subchannels 2 to 24.

Data mapper 12-1 performs error correction encoding on the user data tobe transmitted over the subchannel 1, modulates the user data for eachassigned subcarrier, and thereby generates data symbols. Data mappers12-2 to 12-24 perform similar processing with respect to subchannels 2to 24, respectively.

The multiplexer 13-1 superimposes the data symbols generated by the datamapper 12-1 and the channel estimation symbols generated by thechannel-estimation symbol generator 11-1 onto each subcarrier ofsubchannel 1, and outputs the superimposed subcarriers to the IFFT unit15-1 and the rotator 14-1. The multiplexers 13-2 to 13-24 performsimilar processing with respect to subchannels 2 to 24, respectively.

The rotator 14-1 adds a phase rotation to each subcarrier of subchannel1 based on the control signal output from the scheduler 10, and outputsa result to the IFFT unit 15-2. The rotators 14-2 to 14-24 performsimilar processing with respect to subchannels 2 to 24, respectively.The details of the rotators 14-1 to 14-24 will be explained later.

The IFFT units 15-1 and 15-2 perform inverse fast Fourier transform oneach input subcarrier signal, and thereby convert the frequency-domainsignals into time-domain signals. In the first embodiment, 600subcarriers are used and the point number for the inverse fast Fouriertransform performed by the IFFT units 15-1 and 15-2 is 1024.

The GI inserters and P/S converters 16-1 and 16-2 respectively insertguard intervals for reducing inter-symbol interference into thetime-domain signals converted by the IFFT units 15-1 and 15-2, andconvert the parallel signals into a serial signal to be output.

The D/A converters 17-1 and 17-2 convert the serial signals output fromthe GI inserters and P/S converters 16-1 and 16-2 into analog signals,respectively.

The RF units 18-1 and 18-2 convert the analog signals converted by theD/A converters 17-1 and 17-2 into frequency bands to be transmitted,adjust waves, then transmit the adjusted waves to themulticarrier-signal receiving apparatus through the transmissionantennas 19-1 and 19-2, respectively.

FIG. 2 shows the schematic configuration of the rotator 14-1 accordingto the first embodiment of the present invention. The rotator 14-1includes rotation-amount setting unit 20 a and complex multipliers 21-1a to 21-25 a.

The rotation-amount setting unit 20 a sets thereto phase rotationamounts W1 a to W5 a for every 6 subcarriers where W1 a to W5 a are realnumbers or complex numbers whose absolute values are 1. A group of 6subcarriers to which the same phase rotation amount is added is called asubcarrier group. Based on the scheduling information for eachsubchannel output from the scheduler 10, the rotation-amount settingunit 20 a controls the phase rotation amounts such thatphase-rotation-amount differences among adjacent subcarrier groupsbecome identical when CDTD is used, while the same phase-rotation amountis added to adjacent subcarrier groups (so that there is nophase-rotation amount difference) when CDTD is not used. Alternatively,phase-rotation-amount differences among adjacent subcarrier groups inone or more subchannels may be controlled to be identical.Alternatively, one of subcarrier groups in a subchannel where there isno phase-rotation-amount difference among subcarrier groups in thesubchannel may be regarded as a reference subcarrier group, and a phaserotation amount of the reference subcarrier group may be determinedaccording to a channel condition of the multicarrier-signal receivingapparatus. Alternatively, a unique phase-rotation-amount difference maybe given to each multicarrier-signal transmitting apparatus, and therotation-amount setting unit 20 may add phase rotations to all of thesubcarriers of OFDM symbols using the phase rotation amounts.

Additionally, the number of subcarriers included in a subcarrier groupcan be changed by setting W1 a=W2 a, W3 a=W4 a, and the like.

The complex multipliers (phase rotators) 21-1 a to 21-25 a multiplyinput signals fk1 to fk25 by the phase rotation amounts W1 a to W5 a.The reason that there are 25 input signals (fk1 to fk25) is that 25subcarriers are included in one subchannel since 600 subcarriers areused as 24 subchannels. The reason that the phase rotation amounts (W1 ato W5 a) are determined for every 6 subcarriers is that channelestimation is simplified by equalizing the phase rotation amounts among6 subcarriers since channel estimation subcarriers are inserted intoevery 6 subcarriers. As explained hereinafter, the input signal fk25 isgrouped into a subcarrier group together with the next 5 input signalsfk26 to fk30 (shown in FIG. 3), and the same phase rotation amount W5 ais added thereto.

To equalize phase rotation amounts in a subcarrier group belonging totwo subchannels when 6 subcarriers are grouped into one subcarriergroup, a rotation-amount setting unit 20 b included in the rotator 14-2adjacent to the rotator 14-1 sets a phase rotation amount W1 b to bephase rotation amounts for 5 subcarriers, phase rotation amounts W2 b toW4 b to be phase rotation amounts for respective 6 subcarriers, a phaserotation amount W5 b to be phase rotation amounts for two subcarriers.The phase rotation amount W1 b of the rotator 14-2 is set to beidentical to the phase rotation amount W5 a of the rotator 14-1.

Thus, the number of subcarriers for which the phase rotation amounts W1to W5 are set differs so as to equalize rotation amounts among Msubcarriers when channel estimation subcarriers are inserted into everyM subcarriers.

Hereinafter, an example of phase rotation amounts set by therotation-amount setting unit is explained.

When a phase rotation amount set by the rotation-amount setting unit tothe complex multiplier that adds a phase rotation to a subcarrier k (thek-th subcarrier counted from the smallest frequency) to be transmittedfrom the n-th transmission antenna is denoted as c_(n)(k), therotation-amount setting unit sets, to the complex multiplier, c_(n)(k)determined by Expression (1) where exp (x) represents the x-th power ofthe base of natural logarithm.

c _(n)(k)=exp(−j(ω_(n,SC) SG+θ _(n,SC)))  (1)

(ω_(n,SC) represents a given phase-rotation-amount difference amongsubcarrier groups included in the SC-th subchannel to which the n-thtransmission antenna and subcarrier k belong, and is a positive realnumber (n and SC are positive integers). SG=floor (k/SG_(num))represents a subcarrier group number to which subcarrier k belongs wherefloor (x) represents a positive integer not exceeding x. SG_(num)represents the number of subcarriers included in a subcarrier group(SG_(num)=6 in the first embodiment).

Similarly, SC=floor (k/SC_(num)) represents a subchannel number to whichsubcarrier k belongs. SC_(num) represents the number of subcarriersincluded in a subchannel (SC_(num)=25 in the first embodiment). θ_(n,SC)represents an initial phase of the n-th antenna belonging to asubchannel SC.

When the rotation-amount setting unit sets thereto phase rotationamounts determined by Expression (1) in the case of subcarriers 25 and26 to be transmitted from the antenna 2, subcarrier 25 belongs tosubcarrier group 5 and subchannel 1, subcarrier 26 belongs to subcarriergroup 5 and subchannel 2, and therefore c₂ (25) and c₂ (26) can becalculated as follows.

c ₂(25)=exp(−j(ω_(2,1)·5+θ_(2,1)))

c ₂(26)=exp(−j(ω_(2,2)·5+θ_(2,2)))

When it is assumed that ω_(2,1)=ω and ω_(2,2)=0, then c₂ (25)=c₂ (26)since subcarriers 25 and 26 belong to the same subcarrier group 5. As aresult, 5ω+θ_(2,1)=θ_(2,2). If the initial phase θ_(2,1) is determined,the initial phase θ_(2,2) of adjacent subchannel 2 is uniquelydetermined. c₂ (25) and c₂ (26) correspond to the phase rotation amountW5 a shown in FIG. 2 and the phase rotation amount W1 b shown in FIG. 3,respectively.

In the configuration of the multicarrier-signal transmitting apparatus,a constant phase rotation is added to subcarriers included in asubcarrier group, and a phase difference defined by ω_(n,SC) is addedamong subcarrier groups included in the same subchannel. In other words,a phase rotation amount is set to be constant in a subcarrier group,while a cyclic delay is added to a subchannel using CDTD by setting thephase-rotation-amount difference ω_(n,SC) to an adequate value, and nocyclic delay is added to a subchannel not using CDTD by setting thephase-rotation-amount difference ω_(n,SC) to 0.

Even in the same subchannel, ω_(n,SC) and θ_(n,SC) are changed accordingto the time zone, and the rotation-amount setting unit sets theretovalues acquired by Expression (1). Thereby, a cyclic delay can be addedby setting the phase-rotation-amount difference ω_(n,SC) amongsubcarrier groups to an adequate value, or no cyclic delay can be addedby setting the phase-rotation-amount difference ω_(n,SC) amongsubcarrier groups to 0 for each resource block that is a domainsurrounded by a particular subchannel and time.

An effect caused by setting a phase rotation amount to be constant in asubcarrier group will be explained with an explanation of themulticarrier-signal receiving apparatus.

Although the method of adding phase rotations corresponding to the phaserotation amounts indicated by Expression (1) has been explained,sequences different from Expression (1), such as M (Maximal-length)sequences or PN (Pseudo Noise) sequences such as Gold codes, may beassigned to the phase rotation amounts W1 a to W5 a and W1 b to W5 b foreach subcarrier group that are set by the rotation-amount setting unit,and thereby a phase rotation corresponding to the phase rotation amountmay be added.

FIG. 4 shows an example relationship between a case where OFDMA signalsare grouped into subcarrier groups to be transmitted and the receptionpower received by a terminal when the phase-rotation-amount differenceω_(n,SC) is set to be an adequate value that is not 0.

FIG. 4 (a) shows a state of subcarriers and OFDM symbols beingrespectively arranged along the horizontal and the vertical axesrepresenting frequency and time. Here, only two OFDM symbols are shownin the time direction for simplicity. In this case, the channelestimation symbols P1 to P5 are arranged at every 6 subcarriers.

FIG. 4 (b) shows a state of reception signals being distorted infrequency domains where the horizontal and the vertical axes representfrequency and the reception power.

Since different phase rotations are added to subcarrier groups SG1 toSG4 overlapping subchannel SC1 as explained above, significantdifferences occur among the reception powers of subcarrier groups SG1 toSG4 when the reception powers are compared with one another, and thecorrelation thereamong is small. On the other hand, adjacent channelestimation symbols (for example, P1 and P2) are usually inserted at aninterval by which variation due to channels is sufficiently small, and aconstant phase rotation amount is added to a subcarrier group.Therefore, the reception power hardly varies in a subcarrier group.

Although only the reception power is shown for simplicity, the same canapply to phase. Therefore, data symbols included in a subcarrier groupcan be demodulated using a channel estimation value calculated from achannel estimation symbol included in the subcarrier group when aconstant phase rotation is added to each subcarrier group.

Similar to FIG. 4, FIG. 5 shows an example relationship between a stateof OFDMA signals being grouped into subcarrier groups SG5 to SG7 to betransmitted that are shown in FIG. 5 (a) and the reception powerreceived by a terminal that is shown in FIG. 5 (b).

Although 12 subcarriers are included in each of subcarrier groups SG5 toSG7, the explanation given with reference to FIG. 4 can apply here evenif the number of subcarriers is changed. If operations of channelestimation and channel compensation on the terminal side are considered,the number of subcarriers included in a subcarrier group is preferably amultiple of the subcarrier interval M (M=6 in this case).

FIG. 6 is a schematic block diagram showing the configuration of amulticarrier-signal receiving apparatus according to the firstembodiment. The multicarrier-signal receiving apparatus demodulates datasymbols included in a subcarrier group using a channel estimation valuecalculated from a channel estimation symbol included in the subcarriergroup when a constant phase rotation is added to subcarriers included ineach subcarrier group.

The multicarrier-signal receiving apparatus includes a reception antenna30, an RF (radio frequency) unit 31, an A/D (Analog/Digital) convertor32, a symbol synchronizer 33, an FFT (Fast Fourier Transform) unit 34, acontroller 35, a channel compensator 36, a channel estimator 37, asubchannel extractor 38, and a demodulator 39.

The reception antenna 30 receives signals transmitted from themulticarrier-signal transmitting apparatus.

The RF unit 31 adjusts the signals received by the reception antenna 30so as to lower the frequency to a frequency band applicable to an A/Dconversion.

The A/D convertor 32 converts analog signals into digital signals.

The symbol synchronizer 33 synchronizes OFDM signals.

FFT unit (Fourier transformer) 34 performs fast Fourier transform on thereceived OFDM symbols to acquire each subcarrier signal.

The channel compensator 36 performs channel compensation of dataincluded in the output of the FFT unit 34 based on channel estimationinformation that is an output of the channel estimator 37.

The channel estimator 37 estimates a channel response of each subcarrierfrom channel estimation symbols included in the output of the FFT unit34. As explained later, the channel estimator 37 changes, according toan instruction from the controller 35, a method of calculating a channelestimation value for each subcarrier based on a channel estimation valueacquired from the channel estimation symbol.

The subchannel extractor 38 extracts subchannel signals to bedemodulated by the multicarrier-signal receiving apparatus based onused-subchannel information from the controller 35.

The demodulator 39 demodulates the subchannel signals to be demodulatedthat are extracted by the subchannel extractor 38.

Although an example of the multicarrier-signal receiving apparatus hasbeen shown, the configuration is not limited thereto.

As shown in FIGS. 4 and 5, the bandwidth of the subchannel to bedemodulated is not always identical to the bandwidth of the subcarriergroup. Therefore, the channel estimator 37 performs channel estimationusing channel estimation symbols included in all of the subcarriergroups that include the subchannel to be demodulated. In other words,the channel estimation is performed using the channel estimation symbolsP1 to P5 in the case of subchannel SC1 shown in FIG. 4, and the channelestimation symbols P6 to P11 in the case of subchannel SC2 shown in FIG.5.

Hereinafter, operations of the channel estimator 37 (shown in FIG. 6)are explained with reference to FIGS. 7 and 8. Firstly, a case where thechannel estimator 37 performs averaging in a subcarrier group when achannel estimation value for each subcarrier is calculated is explainedwith reference to FIG. 7.

FIG. 7 (a) shows a state of subcarriers and OFDM symbols beingrespectively arranged along the horizontal and the vertical axesrepresenting frequency and time. As shown in FIG. 7 (a), channelestimation symbols P12 to P17 are arranged at every 6 subcarriers,subchannel SC3 includes 25 subcarriers, and each of subcarrier groupsSG8 to SG10 includes 12 subcarriers.

FIG. 7 (b) shows a state of reception signals being distorted infrequency domains where the horizontal and the vertical axes representfrequency and time. Dashed lines (CSI 1 to CSI 3) represent actualchannel responses. Reference characters x (E1 to E6) represent channelestimation values estimated with the use of the channel estimationsymbols. Solid lines (ECSI1-1 to ECSI1-3) are acquired by averagingchannel estimation values included in the same subcarrier group amongthe channel estimation values E1 to E6 and regarding the averaged valuesas the channel estimation values of the corresponding subcarrier groups.

In other words, subcarrier groups including the subchannel of thebandwidth to be demodulated are considered, and channel estimationsymbols included in the subcarrier groups are used in themulticarrier-signal receiving apparatus. In other words, instead of thechannel estimation symbols P1 to P16 included in subchannel SC3 beingused, the channel estimation symbols P2 to P17 in a wider range areused. This range depends on the relationship between subchannel SC3 andsubcarrier groups SG8 to SG10.

Although amplitudes of the reception signals and the averaged amplitudethereof are shown for simplicity of the drawings, the channel estimationvalues E1 to E6 are actually complex numbers, and the average valueindicates an average of the complex numbers. The complex numbers of thechannel estimation values E1 to E6 may be divided into absolute valuesand arguments, and a complex number acquired by respectively averagingthe absolute values and the arguments may be regarded as the averagevalue.

The channel compensator 36 shown in FIG. 6 performs channel compensationon the data symbols included in each subcarrier group using the averagechannel estimation values ECSI1-1 to ECSI1-3 calculated by the channelestimator 37.

In this manner, channel estimation values are calculated using thechannel estimation values estimated from the channel estimation symbolsincluded not in the subchannel as a unit of demodulation processing, butin the same subcarrier group in which the same phase rotation amount isadded to the subcarriers so as to decrease variation in channelresponses among the subcarriers as much as possible. Thereby, channelestimation values with channel estimation errors due to noise beingsuppressed can be acquired, and enhancement of the receptioncharacteristics can be expected. Additionally, the channel estimationsymbols are arranged separately in the frequency direction. Thereby, thenumber of channel estimation symbols can be reduced, and the utilizationefficiency of bands can be enhanced.

FIG. 8 shows a case where the channel estimator 37 performs (linear)interpolation in a subcarrier group upon channel estimation for eachsubcarrier.

Although FIG. 8 is substantially the same as FIG. 7, solid lines(ECSI2-1 to ECSI2-3) are acquired by performing linear interpolation onchannel estimation values belonging to the same subcarrier group amongthe channel estimation values E7 to E12 and regarding the result aschannel estimation values of subcarriers in the subcarrier group.

Similar to FIG. 7, subcarrier groups SG11 to SG 13 including subchannelSC4 of the bandwidth to be demodulated are considered, and the channelestimation symbols P18 to P23 included in the subcarrier groups are usedin the multicarrier-signal receiving apparatus. In other words, insteadof only the channel estimation symbols P18 to P22 included in subchannelSC4 being used, the channel estimation symbols P18 to P23 in a widerrange are used. This range depends on a relationship between subchannelSC4 and subcarrier groups SG 11 to SG 13.

Although amplitudes of the reception signals and thelinearly-interpolated amplitude thereof are shown for simplicity of thedrawings, the channel estimation values E7 to E12 are actually complexnumbers, and the linear interpolation indicates linear interpolation ofthe complex numbers on a complex plane. The complex numbers of thechannel estimation values E7 to E12 may be divided into absolute valuesand arguments, and a complex number acquired by respectivelylinearly-interpolating the absolute values and the arguments may be usedas the complex number. An interpolation method to be used is not limitedto the linear interpolation, and two-dimensional interpolation orthree-dimensional interpolation may be used.

The channel compensator 36 shown in FIG. 6 performs channel compensationusing the channel estimation values ECSI2-1 to ECSI2-3 interpolated bythe channel estimator 37.

Since channel estimation values are calculated in this manner, channelestimation values following subtle channel variation in each ofsubcarrier groups SG11 to SG13 can be acquired, and channel estimationerrors can be suppressed. Thereby, enhancement of the receptioncharacteristics can be expected. Additionally, the channel estimationsymbols are arranged separately in the frequency direction. Thereby, thenumber of channel estimation symbols can be reduced, and the utilizationefficiency of bands can be enhanced.

If three or more channel estimation symbols are included in onesubcarrier group, the averaging and the linear interpolation may becombined. For example, two average values are acquired from threechannel estimation values, and the two average values can be linearlyinterpolated.

FIGS. 7 and 8 show cases where the channel estimation symbols P12 andP13 included in the subcarrier group SG8 or the channel estimationsymbols P18 and P19 included in the subcarrier group SG11 are includedin the same time section of OFDM symbols (present at the same point intime). As a matter of course, channel estimation values can similarly becalculated using the averaging and the linear interpolation when thesechannel estimation symbols are arranged in different time sections ofOFDM symbols (present at different points in time).

Second Embodiment

Hereinafter, a second embodiment is explained. In the second embodiment,for each resource block that is a domain surrounded by particularsubchannels and time in a frame, the phase rotation amounts added by themulticarrier-signal transmitting apparatus differ among the subcarriergroups at some time and do not differ at another time. Additionally, themulticarrier-signal receiving apparatus performs an interpolation, suchas averaging or a linear interpolation, on channel estimation values ineach subcarrier group or in multiple subcarrier groups. Thereby, channelestimation errors for a subcarrier by which a channel estimation symbolis not transmitted can be suppressed, and channel estimation values areprecisely acquired.

FIG. 9A shows an example of transmitted signals being divided intomultiple resource blocks RB1 to RB9 at given frequency and timeintervals in one frame where the horizontal and the vertical axesrepresent frequency and time. The width of each of the resource blocksRB1 to RB9 in the frequency direction corresponds to that of asubchannel. These resource blocks RB1 to RB9 are transmitted by themulticarrier-signal transmitting apparatus explained in the firstembodiment. In the resource blocks RB2 and RB7, the phase rotationamounts added by the multicarrier-signal transmitting apparatus differamong subcarrier groups. In the resource blocks RB1, RB3 to RB6, RB8,and RB9, the phase rotation amounts added by the multicarrier-signaltransmitting apparatus do not differ among subcarrier groups (thedifference is 0).

Explanations are given in the second embodiment assuming the following.The number of subcarriers included in a subcarrier group and whether ornot phase rotation amounts to be added with respect to resource blocksdiffer among subcarrier groups are preliminarily determined. The contentof the above conditions are stored in the multicarrier-signaltransmitting apparatus and the multicarrier-signal receiving apparatus,and these apparatuses operate based on the stored content. However, themulticarrier-signal transmitting apparatus may determine a phaserotation amount to be added to each subcarrier group included in eachresource block based on whether or not CDTD is used, and indicate to themulticarrier-signal receiving apparatus whether or not the phaserotation amounts differ among subcarrier groups.

FIG. 9B (a) shows an example of subcarriers and OFDM symbols beingarranged along the horizontal and the vertical axes representingfrequency and time. As shown in FIG. 9B (a), channel estimation symbolsP24 to P29 are arranged at every 6 subcarriers. Subchannel SC5 includes25 subcarriers. Each of the subcarrier groups SG14 to SG16 includes 12subcarriers.

FIG. 9B (b) shows an example of reception signals being distorted infrequency domains where the horizontal and the vertical axes representfrequency and time.

FIG. 9B shows a case where there is a phase rotation amount differenceamong subcarrier groups included in subchannel SC5 corresponding to theresource block RB2 or RB7 in which CDTD is used. Similar to FIGS. 7 and8, the averaging or the linear interpolation of channel estimationvalues based on channel estimation symbols included in each subcarriergroup is used as the channel estimating method with respect to thesubcarriers included in subchannel SC5 that is performed by the channelestimator 37.

On the other hand, FIG. 9C (a) shows an example of subcarriers and OFDMsymbols being arranged along the horizontal and the vertical axesrepresenting frequency and time. Similar to FIG. 9B (a), channelestimation symbols P30 to P35 are arranged at every 6 subcarriers.Subchannel SC6 includes 25 subcarriers. Each of subcarrier groups SG17to SG19 includes 12 subcarriers.

FIG. 9C (b) shows an example of the reception signals being distorted infrequency domains where the horizontal and the vertical axes representfrequency and time.

FIG. 9C shows a case where there is no phase rotation amount differenceamong subcarrier groups included in the subchannel SC6 corresponding toany one of the resource blocks RB1, RB3 to RB6, RB8, and RB9. Theaveraging or the linear interpolation of channel estimation values usingthe channel estimation symbols P30 to P35 included in the subcarriergroups SG17 to SG19 is used as the channel estimating method withrespect to the subcarriers included in subchannel SC6 that is performedby the channel estimator 37.

Although a multicarrier-signal receiving apparatus in the secondembodiment is substantially the same as that in the first embodiment,only operations of the controller 35 and the channel estimator 37differ.

In the case of the resource blocks RB2 and RB7 where there is a phaserotation amount difference among the subcarrier groups (in the case ofFIG. 9B), the controller 35 instructs the channel estimator 37 toaverage or linearly interpolate only channel estimation values in thesame subcarrier group similarly to FIGS. 7 and 8 in the firstembodiment. In the case of the resource blocks RB1, RB3 to RB6, RB8, andRB9 (in the case of FIG. 9C), the controller 35 instructs the channelestimator 37 to average or linearly interpolate channel estimationvalues in multiple subcarrier groups.

The channel estimator 37 calculates the channel estimation value of eachsubcarrier using the calculation method according to the instructionfrom the controller 35.

Characteristics that channel responses greatly vary among subcarriergroups in the case of the resource blocks having phase rotation amountdifferences among subcarrier groups, and that channel responses hardlyvary among subcarrier groups in the case of the resource blocks havingno phase rotation amount difference among subcarrier groups areutilized. Thereby, channel estimation errors with respect to eachsubcarrier are suppressed, and channel estimation can be preciselyperformed even when channel estimation symbols are arranged separatelyin the frequency direction.

Third Embodiment

Hereinafter, a third embodiment is explained. In the third embodiment,for each resource block that is a domain surrounded by particularsubchannels and time in a frame, the phase rotation amounts added by themulticarrier-signal transmitting apparatus differ among the subcarriergroups at some time and do not differ at another time according to aphysical channel included in the resource block. Additionally, themulticarrier-signal receiving apparatus performs an interpolation, suchas averaging or a linear interpolation, of channel estimation values ineach subcarrier group or multiple subcarrier groups according to thephysical channel included in the resource block. Thereby, channelestimation values are precisely acquired for subcarriers by which nochannel estimation symbol is transmitted.

FIG. 10A shows an example of transmitted signals being divided intomultiple resource blocks RB11 to RB19 at given frequency and timeintervals in one frame where the horizontal and the vertical axesrepresent frequency and time. The width of each of the resource blocksRB11 to RB19 in the frequency direction corresponds to that of asubchannel. These resource blocks RB11 to RB19 are transmitted by themulticarrier-signal transmitting apparatus explained in the firstembodiment. Since the resource blocks RB12, RB17, and RB18 each includeparticular physical channels (for example, PICH, PCH, or MBMS), phaserotation amounts to be added differ among subcarrier groups. Since theresource blocks RB11, RB13 to RB16, and RB19 do not include particularphysical channels (for example, PICH, PCH, or MBMS), phase rotationamounts to be added by the multicarrier-signal transmitting apparatus donot differ among subcarrier groups (the difference is 0).

The multicarrier-signal transmitting apparatus adds phase rotationamounts that are different among subcarrier groups only to the resourceblocks each including a particular physical channel (for example, PICH,PCH, or MBMS). Here, it is assumed that RB12 includes PICH, and RB17 andRB18 include MBMS.

PCH (Paging Channel) is a downlink common channel and used for paging aterminal. PICH (Paging Indicator Channel) is a downlink common channeland used for indicating, for example, the position of a PCH to aterminal. MBMS (Multimedia Broadcast Multicast Service Channel) is adownlink common channel and used for transmitting, for example, abroadcast signal.

FIG. 10B (a) shows an example of subcarriers and OFDM symbols beingarranged along the horizontal and the vertical axes representingfrequency and time. Channel estimation symbols P36 to P41 are arrangedat every 6 subcarriers. Subchannel SC7 includes 25 subcarriers. Each ofthe subcarrier groups SG20 to SG22 includes 12 subcarriers.

FIG. 10B (b) shows an example of reception signals being distorted infrequency domains where the horizontal and the vertical axes representfrequency and time.

FIG. 10B shows a case where subchannel SC7 corresponds to any one of theresource blocks RB12, RB17, or RB18 each including a particular physicalchannel and therefore having a phase rotation amount difference amongsubcarrier groups. The method explained in FIGS. 7 and 8 is used as thechannel estimating method with respect to the subcarriers included insubchannel SC7 that is performed by the channel estimator 37.

On the other hand, FIG. 10C (a) shows an example of subcarriers and OFDMsymbols being arranged along the horizontal and the vertical axesrepresenting frequency and time. Similar to FIG. 10B (a), channelestimation symbols P42 to P47 are arranged at every 6 subcarriers.Subchannel SC8 includes 25 subcarriers. Each of the subcarrier groupsSG23 to SG25 includes 12 subcarriers.

FIG. 10C (b) shows an example of the reception signals being distortedin frequency domains where the horizontal and the vertical axesrepresent frequency and time.

FIG. 10C shows a case where subchannel SC8 corresponds to any one of theresource blocks RB11, RB13 to RB16, and RB19 each including noparticular physical channel and therefore having no phase rotationamount difference among subcarrier groups. The averaging or the linearinterpolation of channel estimation values using the channel estimationsymbols P42 to P47 included in the subcarrier groups SG23 to SG25 isused as the channel estimating method with respect to the subcarriersincluded in subchannel SC8 that is performed by the channel estimator37.

Although a multicarrier-signal receiving apparatus in the thirdembodiment is substantially the same as that shown in FIG. 6, onlyoperations of the controller 35 and the channel estimator 37 differ.

In the case of the resource blocks RB12, RB17, and RB18 each including aparticular physical channel (for example, PICH or MBMS) (in the case ofFIG. 10B at (a) and (b)), there is difference in phase rotation amountsto be added among the subcarrier groups. The controller 35 instructs thechannel estimator 37 to average or linearly interpolate only channelestimation values in the same subcarrier group similarly to FIGS. 7 and8. In the case of the resource blocks RB11, RB13 to RB16, and RB19 eachincluding no particular physical channel (for example, PICH or MBMS) (inthe case of FIG. 10C at (a) and (b)), there is no difference in phaserotation amounts to be added among subcarrier groups. The controller 35instructs the channel estimator 37 to average or linearly interpolatechannel estimation values in multiple subcarrier groups.

In other words, the controller 35 in the third embodiment controls thechannel estimator 37 based on a physical channel included in theresource block.

The channel estimator 37 calculates a channel estimation value of eachsubcarrier using a calculation method according to the instruction fromthe controller 35.

Characteristics that channel responses greatly vary among subcarriergroups in the case of the resource blocks each including a particularphysical channel and therefore having phase rotation amount differencesamong subcarrier groups, and that channel responses hardly vary amongsubcarrier groups in the case of the resource blocks each including noparticular physical channel and therefore having no phase rotationamount difference among subcarrier groups are used. Thereby, channelestimation errors with respect to each subcarrier are suppressed, andchannel estimation can be precisely performed. At this time, highfrequency-selectivity is enabled in the resource block having adifference in phase rotation amounts to be added among subcarriergroups.

A case where each resource block has a difference in phase rotationamounts to be added by the multicarrier-signal transmitting apparatusamong subcarrier groups or has no difference according to the type of aphysical channel included therein has been shown. However, another casecan be considered where each resource block, even if the same physicalchannel is included therein, has a difference in phase rotation amountsto be added by the multicarrier-signal transmitting apparatus amongsubcarrier groups or has no difference according to the type of atransport channel included therein. The transport channel is a channeldefined by EUTRA (Evolved Universal Terrestrial Radio Access) of 3GPP(3rd Generation Partnership Project), which is provided from a physicallayer to a MAC (Media Access Control) sublayer. There are multiple typesof transport channels to transmit data of different properties ordifferent transmission modes over a physical layer. Different transportchannels are transmitted over the same physical channel in some cases.It can be considered that, for example, SDCH (Shared Data Channel) whichis one type of physical channel includes various transport channels,such as SCH (Downlink Shared Channel) which is a downlink common channeland used for transmitting packet data, and MCH (Multicast Channel) thatis a downlink broadcast channel. In this case, it is considered thatthere is a difference in phase rotation amounts to be added by themulticarrier-signal transmitting apparatus among subcarrier groups or nodifference according to the type of the transport channels.

In the case of the resource block including a particular transportchannel, the controller 35 assumes that there is a difference in phaserotation amounts to be added among subcarrier groups. Then, thecontroller 35 instructs the channel estimator 37 to average or linearlyinterpolate only channel estimation values in the same subcarrier groupas explained in FIGS. 7 and 8. In the case of the resource blockincluding no particular transport channel, the controller 35 assumesthat there is no difference in phase rotation amounts to be added amongsubcarrier groups. Then, the controller 35 instructs the channelestimator 37 to average or linearly interpolate channel estimationvalues in multiple subcarrier groups.

Similarly, another case can be considered where there is a difference inphase rotation amounts to be added by the multicarrier-signaltransmitting apparatus among subcarrier groups according to the type oflogical channels even if a physical channel and a transport channel areincluded equally.

In this case, the controller 35 assumes that there is a difference inphase rotation amounts to be added among subcarrier groups in the caseof the resource block including a particular logical channel. Then, thecontroller 35 instructs the channel estimator 37 to average or linearlyinterpolate only channel estimation values in the same subcarrier groupas explained in FIGS. 7 and 8. In the case of the resource blockincluding no particular logical channel, the controller 35 assumes thatthere is no difference in phase rotation amounts to be added amongsubcarrier groups. Then, the controller 35 instructs the channelestimator 37 to average or linearly interpolate channel estimationvalues in multiple subcarriers. The logical channel is a channel definedby EUTRA of 3GPP, provided by MAC, and determined by the type ofinformation to be transmitted.

The channel-estimation symbol generators 11-1 to 11-24, the data mappers12-1 to 12-24, the multiplexers 13-1 to 13-24, the rotators 14-1 and14-24, and the IFFT units 15-1 and 15-2 that are shown in FIG. 1, andthe FFT unit 34, the controller 35, the channel compensator 36, thechannel estimator 37, and the subchannel extractor 38 that are shown inFIG. 6 may be implemented by dedicated hardware, memories, ormicroprocessors.

Although it has been explained in the first to the third embodimentsthat a subcarrier group includes adjacent subcarriers, the subcarriergroup may include subcarriers that are not arranged adjacent to oneanother. For example, a subcarrier group may include subcarriersseparated from one another by one subcarrier or two carriers, or includemultiple pairs of subcarriers, each pair of which is separated from oneanother by two subcarriers. When a subcarrier group includes 6subcarriers separated from one another by one subcarrier, each phaserotation amount set by the rotation-amount setting unit 20 a is outputto the complex multipliers that add phase rotations to the subcarriersthat are included in each subcarrier group and separated from oneanother by one subcarrier. In other words, the complex multipliersreceiving the phase rotation amount W1 a are the complex multipliers21-1 a, 21-3 a, 21-5 a, 21-7 a, 21-9 a, and 21-11 a.

Although embodiments of the present invention have been explained indetail with reference to the accompanying drawings, the specificconfiguration is not limited to these embodiments, and variousmodifications can be made without departing from the scope of thepresent invention.

INDUSTRIAL APPLICABILITY

The present invention is preferably used for a multicarrier-signaltransmitting apparatus and a multicarrier-signal receiving apparatus forcellular phones and base stations thereof, but not limited thereto.

1. A multicarrier-signal transmitting apparatus comprising: arotation-amount setting unit configured to set a phase rotation amountfor each subcarrier of a plurality of subcarrier groups, the phaserotation amount being set with a setting selected from a first settingand a second setting, the first setting being such that the phaserotation amount is capable to be different between a subcarrier groupand an adjacent subcarrier group within a plurality of adjacentsubcarrier groups, and the second setting being such that the phaserotation amount is identical between a subcarrier group and an adjacentsubcarrier group within a plurality of adjacent subcarrier groups; and aphase rotator configured to add a phase rotation to reference signalsand a data signal of said each subcarrier of said plurality ofsubcarrier groups based on the phase rotation amount.
 2. Themulticarrier-signal transmitting apparatus according to claim 1, whereinthe rotation-amount setting unit is further configured to determine thephase rotation amount based on types of physical channels, transportchannels or logical channels.
 3. A multicarrier-signal transmittingmethod comprising: setting a phase rotation amount for each subcarrierof a plurality of subcarrier groups, the phase rotation amount being setwith a setting selected from a first setting and a second setting, thefirst setting being such that the phase rotation amount is capable to bedifferent between a subcarrier group and an adjacent subcarrier groupwithin a plurality of adjacent subcarrier groups, and the second settingbeing such that the phase rotation amount is identical between asubcarrier group and an adjacent subcarrier group within a plurality ofadjacent subcarrier groups; and adding a phase rotation to referencesignals and a data signal of said each subcarrier of said plurality ofsubcarrier groups based on the phase rotation amount.
 4. Themulticarrier-signal transmitting method according to claim 3, furthercomprising: determining the phase rotation amount based on types ofphysical channels, transport channels or logical channels.
 5. Anon-transitory computer-readable medium having instructions storedthereon, such that when the instructions are read and executed by aprocessor, the processor is configured to perform the steps of: settinga phase rotation amount for each subcarrier of a plurality of subcarriergroups, the phase rotation amount being set with a setting selected froma first setting and a second setting, the first setting being such thatthe phase rotation amount is capable to be different between asubcarrier group and an adjacent subcarrier group within a plurality ofadjacent subcarrier groups, and the second setting being such that thephase rotation amount is identical between a subcarrier group and anadjacent subcarrier group within a plurality of adjacent subcarriergroups; and adding a phase rotation to reference signals and a datasignal of said each subcarrier of said plurality of subcarrier groupsbased on the phase rotation amount.
 6. The non-transitorycomputer-readable medium according to claim 5, further comprising:determining the phase rotation amount based on types of physicalchannels, transport channels or logical channels.